1. Field of the Invention
This invention relates to an organohybrid-based damping material and a method for producing the same, more particularly a damping material comprising a piezoelectric, dielectric and electroconductive material and an organic high-molecular-weight matrix material, which efficiently absorbs noise and vibrational energy from the outside and releases it as thermal energy to damp noise and vibrational energy, and a method for producing the same.
The present invention provides a novel damping material, different from the conventional ones, which is applicable to wide areas, including electric appliances, machines, chemistry, construction/civil engineering, and transportation.
2. Description of the Related Art
Normal measures against noise produced by, e.g., home electric appliances and vehicles, especially while they are running on highways and bridges, are thick walls of inorganic materials. Increasing their weight will more efficiently reduce noise. On the other hand, porous fibers (e.g., rock wool and glass wool) have been used to decrease weight of sound and vibration insulating materials. Sound insulating walls are double-structured to reduce weight of the walls. Damping materials have been also developed, e.g., high-molecular-weight materials which directly convert mechanical vibrational energy into thermal energy by the internal viscous and frictional effects, and inorganic ceramic piezoelectric materials which convert vibrational energy into electric energy.
These measures have their own disadvantages. Increasing thickness or weight of sound insulating walls of inorganic materials needs high costs and special structural considerations. On the other hand, inorganic materials for reducing wall weight, e.g., rock wool, glass wool and other porous fibers, have insufficient damping efficiency in a low frequency region, because of their low loss tangent (tan"sgr") of 0.5 or so at the highest. Double-structured walls for reducing wall weight may have reduced sound transmission loss at a specific frequency, resulting from the resonance produced by the wall masses and air spring between them, causing insufficient sound insulation. High-molecular-weight damping materials have been rarely commercialized, because they try to absorb mechanical energy from the outside based on their own glass transition point, and can absorb noise and vibrational energy from the outside only at around their glass transition point, unable to sufficiently absorb high noise and vibrational energy over a desired temperature range.
It is an object of the present invention to provide, under these situations, an organohybrid-based damping material capable of efficiently absorbing noise and vibrational energy from the outside and releasing it as thermal energy, and also to provide a method for producing the same.
It is another object of the present invention to provide a damping material showing a high maximum loss tangent (tan"sgr") over a wide temperature range.
The inventors of the present invention have noticed, after having extensively studied to solve the above problems, that energy is transmitted through a molecule and also between molecules, the former traveling much more efficiently and at a higher speed and being absorbed more efficiently. We have noted that it is important to bind an additive to the polymer at adequate sites and by adequate strength through a chemical bond which is stronger than van der Waals force, e.g., hydrogen bond or bond given by a radical or ionic reaction, rather than merely mixing them, and found a very good energy damping material working on a new principle that a composite of an organic polymer matrix material incorporated with a compound exhibiting piezoelectric, dielectric and electroconductive effects absorbs vibrational energy from the outside as an electric potential to be consumed as Joule heat by the inside electroconductive circuit, reaching the present invention.
The first invention is a composite damping material, obtained by at least mixing a material showing piezoelectric, dielectric and electroconductive effects with an organic polymer matrix material having a polar side chain, wherein the material showing piezoelectric, dielectric and electroconductive effects is a compound shown by the following general formula (I): 
wherein,
(1) R1 and R2 are each a hydrocarbon group having a carbon number of 1 to 10, and may be the same or different,
(2) (m) and (mxe2x80x2) are an integer of 1 or 2, and may be the same or different,
(3) (n) and (nxe2x80x2) are an integer of 0 to 3, and may be the same or different,
(4) (s) and (t) are an integer of 1 to 3, and may be the same or different, and
(5) X is at least one bonding group selected from the group consisting of oxygen, sulfur and a halogen, or a hydrocarbon group, which may contain at least one of the above atoms, having a carbon number of 1 to 20 and a group containing an ester linkage.
The second invention is a method for producing a composite damping material composed of a material showing piezoelectric, dielectric and electroconductive effects and an organic polymer matrix material, comprising the following two steps (a) and (b):
Step(a)
a step of mixing a material showing piezoelectric, dielectric and electroconductive effects with an organic polymer matrix material at normal temperature or higher, and
Step(b)
a step for forming the mixture obtained by Step (a) by pressing or drawing at 100 to 170xc2x0 C.